NASCAR has changed a great deal in the last 20 years. Behind the Wall, which chronicles Terry Labonte’s 1991 season, gives the reader a sense of just how much.

I’m reading a book called Behind the Wall: A Season on the NASCAR Circuit. Written by Richard Huff, who still covers NASCAR for the New York Daily News, the book follows Terry Labonte and his Sunoco team as it meanders through the 1991 Winston Cup season.

The book is interesting on any number of levels, and not simply because it reminds you of the insane escalation of costs in the sport, though that is an eye-opener: in 1988, Sunoco paid $750,000 to sponsor a car for 28 races. Today, a primary will pay in the neighborhood of $20 million for the 36-race season.

However, the book is even more valuable in demonstrating how the sport has fundamentally changed in the last 20 years.

Behind the Wall opens on the July race at Daytona, where a frustrated Labonte parked his car less than 10 laps in — there was nothing wrong with the car, no mechanical problem to prevent Labonte from racing; it was just bad. So, Labonte parked it. And left the track.

The idea that any driver, let alone a former champion (Labonte won his first title in 1984 and would win another in 1996) could get away with a stunt like that today is almost inconceivable — remember the torrents of disapproval directed at Kyle Busch two years ago when he left the track after a wreck (and he was replaced for the remainder of the race by Dale Earnhardt Jr.)?

And yet, that a driver could get away with that conduct 17 years ago still isn’t the single most interesting thing I’ve read thus far. This is:

A typical green flag stop for gas and four tires takes about 22.5 seconds for the better teams.

A typical green flag stop today, for a better team, is closer to 14.5 seconds. And while perhaps some of this improvement is attributable to simple advances in technology, it’s an even safer bet that this change owes itself to simple professionalism. Not your father’s NASCAR, indeed.